Weak tracking messenger

Microsoft.Toolkit.Mvvm/ComponentModel/ObservableRecipient.cs

@@ -26,11 +26,11 @@ public abstract class ObservableRecipient : ObservableObject
  /// Initializes a new instance of the <see cref="ObservableRecipient"/> class.
  /// </summary>
  /// <remarks>
- /// This constructor will produce an instance that will use the <see cref="Messaging.Messenger.Default"/> instance
+ /// This constructor will produce an instance that will use the <see cref="WeakReferenceMessenger.Default"/> instance
  /// to perform requested operations. It will also be available locally through the <see cref="Messenger"/> property.
  /// </remarks>
  protected ObservableRecipient()
- : this(Messaging.Messenger.Default)
+ : this(WeakReferenceMessenger.Default)
  {
  }
 
@@ -79,7 +79,7 @@ public bool IsActive
  /// <remarks>
  /// The base implementation registers all messages for this recipients that have been declared
  /// explicitly through the <see cref="IRecipient{TMessage}"/> interface, using the default channel.
- /// For more details on how this works, see the <see cref="MessengerExtensions.RegisterAll"/> method.
+ /// For more details on how this works, see the <see cref="IMessengerExtensions.RegisterAll"/> method.
  /// If you need more fine tuned control, want to register messages individually or just prefer
  /// the lambda-style syntax for message registration, override this method and register manually.
  /// </remarks>

Microsoft.Toolkit.Mvvm/Messaging/IMessenger.cs

@@ -64,12 +64,12 @@ public delegate void MessageHandler<in TRecipient, in TMessage>(TRecipient recip
  /// Messenger.Default.Register(this, Receive);
  /// </code>
  /// The C# compiler will automatically convert that expression to a <see cref="MessageHandler{TRecipient,TMessage}"/> instance
- /// compatible with <see cref="MessengerExtensions.Register{TRecipient,TMessage}(IMessenger,TRecipient,MessageHandler{TRecipient,TMessage})"/>.
+ /// compatible with <see cref="IMessengerExtensions.Register{TRecipient,TMessage}(IMessenger,TRecipient,MessageHandler{TRecipient,TMessage})"/>.
  /// This will also work if multiple overloads of that method are available, each handling a different
  /// message type: the C# compiler will automatically pick the right one for the current message type.
  /// It is also possible to register message handlers explicitly using the <see cref="IRecipient{TMessage}"/> interface.
  /// To do so, the recipient just needs to implement the interface and then call the
- /// <see cref="MessengerExtensions.RegisterAll(IMessenger,object)"/> extension, which will automatically register
+ /// <see cref="IMessengerExtensions.RegisterAll(IMessenger,object)"/> extension, which will automatically register
  /// all the handlers that are declared by the recipient type. Registration for individual handlers is supported as well.
  /// </summary>
  public interface IMessenger

Microsoft.Toolkit.Mvvm/Messaging/MessengerExtensions.cs → Microsoft.Toolkit.Mvvm/Messaging/IMessengerExtensions.cs

@@ -8,19 +8,20 @@
 using System.Linq.Expressions;
 using System.Reflection;
 using System.Runtime.CompilerServices;
+using Microsoft.Toolkit.Mvvm.Messaging.Internals;
 
 namespace Microsoft.Toolkit.Mvvm.Messaging
 {
  /// <summary>
  /// Extensions for the <see cref="IMessenger"/> type.
  /// </summary>
- public static partial class MessengerExtensions
+ public static class IMessengerExtensions
  {
  /// <summary>
  /// A class that acts as a container to load the <see cref="MethodInfo"/> instance linked to
  /// the <see cref="Register{TMessage,TToken}(IMessenger,IRecipient{TMessage},TToken)"/> method.
  /// This class is needed to avoid forcing the initialization code in the static constructor to run as soon as
- /// the <see cref="MessengerExtensions"/> type is referenced, even if that is done just to use methods
+ /// the <see cref="IMessengerExtensions"/> type is referenced, even if that is done just to use methods
  /// that do not actually require this <see cref="MethodInfo"/> instance to be available.
  /// We're effectively using this type to leverage the lazy loading of static constructors done by the runtime.
  /// </summary>
@@ -32,7 +33,7 @@ private static class MethodInfos
  static MethodInfos()
  {
  RegisterIRecipient = (
- from methodInfo in typeof(MessengerExtensions).GetMethods()
+ from methodInfo in typeof(IMessengerExtensions).GetMethods()
  where methodInfo.Name == nameof(Register) &&
  methodInfo.IsGenericMethod &&
  methodInfo.GetGenericArguments().Length == 2

Microsoft.Toolkit.Mvvm/Messaging/Microsoft.Collections.Extensions/DictionarySlim{TKey,TValue}.cs → Microsoft.Toolkit.Mvvm/Messaging/Internals/Microsoft.Collections.Extensions/DictionarySlim{TKey,TValue}.cs

@@ -130,7 +130,11 @@ public void Clear()
  this.entries = InitialEntries;
  }
 
- /// <inheritdoc cref="Dictionary{TKey,TValue}.ContainsKey"/>
+ /// <summary>
+ /// Checks whether or not the dictionary contains a pair with a specified key.
+ /// </summary>
+ /// <param name="key">The key to look for.</param>
+ /// <returns>Whether or not the key was present in the dictionary.</returns>
  public bool ContainsKey(TKey key)
  {
  Entry[] entries = this.entries;
@@ -176,7 +180,18 @@ public bool TryGetValue(TKey key, out TValue? value)
  }
 
  /// <inheritdoc/>
- public bool TryRemove(TKey key, out object? result)
+ public bool TryRemove(TKey key)
+ {
+ return TryRemove(key, out _);
+ }
+
+ /// <summary>
+ /// Tries to remove a value with a specified key, if present.
+ /// </summary>
+ /// <param name="key">The key of the value to remove.</param>
+ /// <param name="result">The removed value, if it was present.</param>
+ /// <returns>Whether or not the key was present.</returns>
+ public bool TryRemove(TKey key, out TValue? result)
  {
  Entry[] entries = this.entries;
  int bucketIndex = key.GetHashCode() & (this.buckets.Length - 1);

Microsoft.Toolkit.Mvvm/Messaging/Microsoft.Collections.Extensions/IDictionarySlim{TKey}.cs → Microsoft.Toolkit.Mvvm/Messaging/Internals/Microsoft.Collections.Extensions/IDictionarySlim{TKey}.cs

@@ -17,8 +17,7 @@ internal interface IDictionarySlim<in TKey> : IDictionarySlim
  /// Tries to remove a value with a specified key, if present.
  /// </summary>
  /// <param name="key">The key of the value to remove.</param>
- /// <param name="result">The removed value, if it was present.</param>
- /// <returns>.Whether or not the key was present.</returns>
- bool TryRemove(TKey key, out object? result);
+ /// <returns>Whether or not the key was present.</returns>
+ bool TryRemove(TKey key);
  }
 }

Microsoft.Toolkit.Mvvm/Messaging/Internals/Type2.cs

@@ -0,0 +1,79 @@
+using System;
+using System.Runtime.CompilerServices;
+
+namespace Microsoft.Toolkit.Mvvm.Messaging.Internals
+{
+ /// <summary>
+ /// A simple type representing an immutable pair of types.
+ /// </summary>
+ /// <remarks>
+ /// This type replaces a simple <see cref="ValueTuple{T1,T2}"/> as it's faster in its
+ /// <see cref="GetHashCode"/> and <see cref="IEquatable{T}.Equals(T)"/> methods, and because
+ /// unlike a value tuple it exposes its fields as immutable. Additionally, the
+ /// <see cref="TMessage"/> and <see cref="TToken"/> fields provide additional clarity reading
+ /// the code compared to <see cref="ValueTuple{T1,T2}.Item1"/> and <see cref="ValueTuple{T1,T2}.Item2"/>.
+ /// </remarks>
+ internal readonly struct Type2 : IEquatable<Type2>
+ {
+ /// <summary>
+ /// The type of registered message.
+ /// </summary>
+ public readonly Type TMessage;
+
+ /// <summary>
+ /// The type of registration token.
+ /// </summary>
+ public readonly Type TToken;
+
+ /// <summary>
+ /// Initializes a new instance of the <see cref="Type2"/> struct.
+ /// </summary>
+ /// <param name="tMessage">The type of registered message.</param>
+ /// <param name="tToken">The type of registration token.</param>
+ [MethodImpl(MethodImplOptions.AggressiveInlining)]
+ public Type2(Type tMessage, Type tToken)
+ {
+ TMessage = tMessage;
+ TToken = tToken;
+ }
+
+ /// <inheritdoc/>
+ [MethodImpl(MethodImplOptions.AggressiveInlining)]
+ public bool Equals(Type2 other)
+ {
+ // We can't just use reference equality, as that's technically not guaranteed
+ // to work and might fail in very rare cases (eg. with type forwarding between
+ // different assemblies). Instead, we can use the == operator to compare for
+ // equality, which still avoids the callvirt overhead of calling Type.Equals,
+ // and is also implemented as a JIT intrinsic on runtimes such as .NET Core.
+ return
+ TMessage == other.TMessage &&
+ TToken == other.TToken;
+ }
+
+ /// <inheritdoc/>
+ public override bool Equals(object? obj)
+ {
+ return obj is Type2 other && Equals(other);
+ }
+
+ /// <inheritdoc/>
+ [MethodImpl(MethodImplOptions.AggressiveInlining)]
+ public override int GetHashCode()
+ {
+ unchecked
+ {
+ // To combine the two hashes, we can simply use the fast djb2 hash algorithm.
+ // This is not a problem in this case since we already know that the base
+ // RuntimeHelpers.GetHashCode method is providing hashes with a good enough distribution.
+ int hash = RuntimeHelpers.GetHashCode(TMessage);
+
+ hash = (hash << 5) + hash;
+
+ hash += RuntimeHelpers.GetHashCode(TToken);
+
+ return hash;
+ }
+ }
+ }
+}

Microsoft.Toolkit.Mvvm/Messaging/Internals/Unit.cs

@@ -0,0 +1,31 @@
+using System;
+using System.Runtime.CompilerServices;
+
+namespace Microsoft.Toolkit.Mvvm.Messaging.Internals
+{
+ /// <summary>
+ /// An empty type representing a generic token with no specific value.
+ /// </summary>
+ internal readonly struct Unit : IEquatable<Unit>
+ {
+ /// <inheritdoc/>
+ [MethodImpl(MethodImplOptions.AggressiveInlining)]
+ public bool Equals(Unit other)
+ {
+ return true;
+ }
+
+ /// <inheritdoc/>
+ public override bool Equals(object? obj)
+ {
+ return obj is Unit;
+ }
+
+ /// <inheritdoc/>
+ [MethodImpl(MethodImplOptions.AggressiveInlining)]
+ public override int GetHashCode()
+ {
+ return 0;
+ }
+ }
+}